1. Field of the Invention
This invention relates to a rotation-speed sensor device and more particularly to a rotation-speed sensor device used for detecting the rpm of the wheels of an automobile.
The present invention relates to a double row rolling bearing with a sensor unit for rotatively supporting a wheel of a rolling stock or an automobile or a rotation shaft of a mill for metal working to a housing or a suspension system which does not rotate even at the time of use, and detecting a state of the double row rolling bearing portion. The double row rolling bearing with a sensor unit is effective for detecting a rotating speed of a wheel, a rotating shaft or the like, and a state of the double row rolling bearing (temperature, oscillation or the like) so as to judge existence/inexistence of error or abnormality of the double row rolling bearing portion.
2. Description of the Related Art
In order to control an anti-lock brake system (ABS) or traction control system (TCS) in order to maintain the stability and steadiness of an automobile when braking or accelerating, it is necessary to detect the rpm of the wheels. Recently, a rotation-speed sensor device is built into a rolling-bearing unit for supporting the wheels to rotate freely with respect to the suspension, and such a rolling bearing unit with rotation-speed sensor device is widely used for supporting the wheels such that they rotate freely with respect to the suspension and for detecting the rpm of the wheels.
A rolling-bearing unit with rotation-speed sensor device that is used for this purpose and having a structure as shown in FIG. 18 and FIG. 19 is disclosed in Japanese Patent Publication No. Tokukai Hei 11-23596.
The first example of prior construction of a rolling bearing unit 1 with rotation-speed sensor device shown in FIG. 18 comprises a rotation-speed sensor device 3 built into the rolling-bearing unit 2. In the rolling-bearing unit 2, a hub 5 and inner race 6, which form a rotating race, are supported such that they rotate freely on the inner-diameter side of an outer race 4, which is the stationary race. A first flange 7 for attaching to the wheel is formed around the outer peripheral surface on the outside end of this hub 5 (which is the end on the outside in the width direction when installed in the vehicle, and is the left end in all of the drawings of the rolling-bearing unit. This is the same throughout the explanation of this invention), and a first inner-ring raceway 8 is formed around the outer peripheral surface in the middle of the hub 5.
Moreover, the inner race 6 has a second inner-ring raceway 9 formed around its outer peripheral surface and located at a portion closer to the inside end of the hub 5 (which is the end on the inside in the width direction when installed in the vehicle, and is the right end in all of the drawings of the rolling-bearing unit. This is the same throughout the explanation of this invention) and it fits around a stepped section 10 that has a diameter a little less than that of the section where the first inner-ring raceway 8 is formed. Also, a first outer-ring raceway 11 that faces the first inner-ring raceway 8, and a second outer-ring raceway 12 that faces the second inner-ring raceway 9 are formed around the inner peripheral surface of the outer race 4, and a second flange 13 for supporting the outer race 4 on the suspension is formed around the outer peripheral surface of the outer race 4.
Moreover, a plurality of rolling elements 14 are located between the first and second inner-ring raceways 8, 9 and the first and second outer-ring raceways 11, 12, and they support the hub 5 and inner race 6 such that they rotate freely on the inner-diameter side of the outer race 4. With the inner race 6 fitted around the stepped section 10, a nut 15 screws onto a male screw section that is formed on the inside end of the hub 5 and retains the inner race 6 in order to prevent the inner race 6 and hub 5 from coming apart.
Furthermore, a cover 16 covers the opening on the inside end (right end in FIG. 18) of the outer race 4. This cover 16 comprises a main piece 17 that is cylindrical shaped with a bottom and that is formed by injection molding of synthetic resin or plastic, and a metal cylindrical fitting section 18 that is connected to the opening section of the main piece 17. This cylindrical fitting section 18 is connected to the opening section of the main piece 17 by molding its base end at the time when the main piece 17 is being formed by injection molding. This cover 16, formed in this way, covers the opening on the inside end of the outer race 4 by securely interference-fitting the tip end half (left half in FIG. 18) of the cylindrical fitting section 18 around the inside end of the outer race 4.
On the other hand, the encoder 19 of the rotation-speed sensor device fits around the outer peripheral surface of the inside end of the inner race 6, which fits around the inside end of the hub 5, in the section that is separated from the second inner-ring raceway 9. This encoder 19 comprises a support ring 20 and permanent magnet 21. Of these, the support ring 20 is formed into a circular ring shape having an L-shaped cross section by bending a magnetic metal sheet such as SPCC, and it interference-fits tightly around the inside end of the inner race 6.
Also, the permanent magnet 21 is made by attaching rubber, which has been mixed with ferrite powder or the like, to the inside surface of the circular ring portion of the support ring 20 by burn-in etc. This permanent magnet 21 is magnetically oriented in the axial direction (left and right in FIG. 18), and the direction of magnetic poles alternates at equal intervals around in the circumferential direction. Therefore, the S pole and N pole are arranged such that they alternate at equal intervals around the circumference of the inside surface of the encoder 19, which is the detected section.
Moreover, an insertion hole 22 is formed in the main piece 17 of the cover 16 in the part that faces the inside surface of the permanent magnet 21 of the encoder 19 such that it penetrates the main piece 17 in the axial direction of the cover 16. A sensor 23 is inserted inside this insertion hole 22. This sensor 23 comprises: an IC, having a magnet-detection element such as a hall element or magnetic-resistance element (MR element), whose characteristics change according to the direction of flow of magnetic flux, and a wave-shaping circuit for adjusting the waveform output from this magnet detection element; and a pole-piece made of magnetic material for guiding the magnetic flux output from the permanent magnet 21 (or flowing to the permanent magnet 21) to the magnet detection element, which are embedded in synthetic resin or plastic.
This kind of sensor 23 is formed at a portion closer to the tip end (left end in FIG. 18), and it comprises: a column-shaped insert section 24 that can be snugly inserted inside the insertion hole 22, and an outward facing flange-shaped edge section 25 that is formed around the base end (right end in FIG. 18) of the insert section 24. There is a fitting groove formed around the outer peripheral surface in the middle of the insert section 24 and an O-ring 26 fits in this fitting groove.
On the other hand, a fitting cylinder 28 is formed through part of the outside surface of the cover 16 (the surface that is on opposite side from the space 27 where the rolling elements 14 are located, or the right side surface in FIG. 18) in the section around the opening of the insertion hole 22. When the insert section 24 is inserted inside the fitting cylinder 28 and the flange-shaped edge section 25 comes in contact with the tip end surface of the fitting cylinder 28, the sensor 23 is connected to and supported by this fitting cylinder 28 by a fitting spring 29. A connection and support structure using this kind of fitting spring 29 is disclosed in detail in Japanese Patent Publication No. Tokukai Hei 11-23596, and since it is not related to this invention, a detailed drawing and explanation have been omitted.
When using the rolling bearing unit 1 with rotation-speed sensor device described above, the second flange 13 that is formed around the outer peripheral surface of the outer race 4 is connected to and supported by the suspension by bolts (not shown in the figure), and the wheel is fastened by studs 30 to the first flange 7 that is formed around the outer peripheral surface of the hub 5, the studs 30 being provided in the first flange 7, and the wheel is supported so as to rotate freely with respect to the suspension. In this state, as the wheel rotates, the N pole and S pole that are located on the inside surface of the permanent magnet 21 alternately pass by the area near the end surface of the detection section of the sensor 23. As a result, the direction of the magnetic flux flowing inside the sensor 23 changes, and the output of the sensor 23 changes. The frequency at which the output of the sensor 23 changes in this way is proportional to the rpm of the wheel. Therefore, by sending the output from the sensor 23 to a controller (not shown in the figures), it is possible properly control the ABS or TCS.
Moreover, in the case of a second example of prior art construction that is disclosed in Japanese Patent Publication No. Tokukai Hei 11-23596, a cylindrical section 31 is formed on the inside end of the hub 5, and a crimped section 34 is formed on the tip end of this cylindrical section 31 by crimping a portion of the tip end that protrudes from the inside surface of the inner race 6 outward in the radial direction, and the inner race 6 is fastened to the hub 5 by this crimped section 34. By using this kind of construction, in comparison with the construction of fastening the inner race 6 to the hub 5 with a nut 15 as in the case of the first example of prior art construction shown in FIG. 18, it is possible to reduce the cost by reducing the number of parts and the amount of work necessary for assembly. In the case of the second example of prior art construction shown in FIG. 19, the construction of the part that connects and supports the sensor 23 in the fitting cylinder 28, which is formed in the main piece 17 of the cover 16, by the fitting spring 29, is different than in the case of the first example described above. The construction of connecting and supporting using a fitting spring 29 is also described in detail in Japanese Patent Publication No. Tokukai Hei 11-23596, and since it is also not related to this invention, detailed drawings and explanation are omitted.
Moreover, in the case of the second example of prior art construction, the encoder 19 is also different than that of the first example. That is, the encoder 19 is formed generally into an annular shape by bending magnetic metal sheet such as carbon steel plate in an L-shaped cross section such that a circular-ring section 32 is formed. A plurality of penetrating holes 33 is formed in this circular-ring section 32 in order that the magnetic characteristics of this circular-ring section 32 change alternately at equal intervals around the circumferential direction. To correspond with this, the internal construction of the sensor 23 is also different than that the first example.
The prior art construction shown in FIG. 18 and FIG. 19 is such that the detection signal from either of the sensors 23 is sent to a controller located on the automobile chassis side via a harness 35. On the other hand, construction of sending the detection signal from the rotation-speed detection sensor to a controller on the automobile chassis side via wireless transmission is disclosed in Japanese Patent Publication No. Tokukai 2001-151090. In other words, with a transmitter unit for wireless transmission of the detection signal located around the outer peripheral surface of the stationary or outer race next to the rotation-speed detection sensor, there is no need for a harness for transmitting this detection signal. In addition, with this kind of construction, together with preventing trouble due to harness wires that are cut by flying rocks or the like, it is possible to do away with the need for the harness and the work of wiring the harness, thus making it possible to reduce the weight and cost of the apparatus.
In the case of the prior art construction disclosed in Japanese Patent Publication No. Tokukai 2001-151090, no special consideration has been taken for detecting whether or not there is an error in the rotation-speed detection sensor or the transmitter unit located in the rolling-bearing unit for supporting the wheel to prevent faulty operation of the ABS or TCS. On the other hand, by using construction in which the detection signal is sent wirelessly, there are more causes for erroneous detection signal than with construction using a harness, such as maintaining power for transmission. Also, in the case of new construction for performing wireless transmission, it is not possible to use the prior art construction of using a harness for signal and power transmission as is.
The double row rolling bearing with a sensor unit is effective for detecting a rotating speed of a wheel, a rotating shaft or the like, and a state of the double row rolling bearing (temperature, oscillation or the like) so as to judge existence/inexistence of error or abnormality in the double row rolling bearing portion.
On the other hand, with the double row rolling bearing widely used in order to rotatively support a rotating member such as a wheel to a fixed member such as a suspension system, there has been suggested that rotating speed or vibration of the rotating member such as a wheel is detected by providing a rotating speed sensor or an acceleration sensor to the double row rolling bearing, part of which has been carried out in practice. For example, as shown in FIGS. 38 and 39. Japanese Utility Model Publication No. Jitsukai Hei 5-12744 (Utility Model Registration No. 2543369) describes a structure in which an acceleration sensor 2 and a rotation detection sensor 3 are installed into a double row rolling bearing 1. Moreover, Japanese Patent Publication No. Tokuhyo 2001-500597 (Specification of U.S. Pat. No. 6,161,962) also describes a similar structure.
In the case of the conventional structure described in Japanese Utility Model Publication No. Jitsukai Hei 5-12744, an inner race 7 is rotatively supported to an inner diameter side of an outer race 5 via a plurality of rolling elements 8 between them. Double row inner-ring raceways 6 are provided on an outer peripheral surface of the inner race 7. Double row outer-ring raceways 4 are provided on an inner peripheral surface of the outer race 5. A circular ring 10 to be detected is externally fitted to an end portion of the inner race 7. The acceleration sensor 2 and the rotation detecting sensor 3 are held in a cover 9 mounted to an opening at the end portion of the outer race 5, and the rotation detecting sensor 3 has a detecting section which is opposed to the ring 10 to be detected.
With respect to the acceleration sensor 2 and the rotation detecting sensor 3, a detecting signal of the acceleration sensor 2 is utilized for obtaining vibration generated on the double row rolling bearing 1 so as to know the end of the lifetime of the double row rolling bearing 1. Moreover, a detecting signal of the rotation detecting sensor 3 is utilized for obtaining rotating speed of the wheel supported by the double row rolling bearing 1 so as to control an antilock brake system (ABS) and a traction control system (TCS).
The structures shown in FIGS. 38 and 39 relate to a double row rolling bearing for an automobile, but in the case of a double row rolling bearing for a rolling stock, a running speed is obtained and another state values such as temperature can be detected. The running speed is necessary for making skidding control for preventing a wheel from being worn unevenly, and the temperature is necessary for preventing the double row rolling bearing from being seized. For this reason, a rotating and supporting system with a sensor for a rolling stock shown in FIGS. 40 and 41 has been conventionally known.
In a state that a wheel, not shown, is supported to be fixed, an axle 11 which rotates at the time of use is rotatively supported to an inner diameter side of a bearing housing 12 which does not rotate at the time of use by a double row rolling bearing 1. The double row rolling bearing 1 is a double row tapered roller bearing and it has an outer race 5 and an inner ring 7 which are arranged coaxially, and a plurality of rolling elements 8 which are tapered rollers. The rolling elements 8 are provided between a double row outer-ring raceway 4 formed on an inner peripheral surface of the outer race 5 and a double row inner ring raceway 6 formed on an outer peripheral surface of the inner ring 7 so as to be freely rolling in a state that they are retained by a retainer 13.
The outer race 5 in the double row rolling bearing 1 is internally retained to the bearing housing 12. Meanwhile, the inner race 7 comprises a pair of inner ring elements 14 and a spacer such that the spacer 15 is axially sandwiched between the pair of inner ring elements 14a, 14b, and the inner ring 7 is externally fitted to a portion closer to one end (left end in FIG. 40) of the axle 11. Moreover, an annular member 16 which is called as an oil thrower is externally fitted to a portion of the end of the axle 11 which is protruded further than the inner ring element 14a on an axially outer side. Moreover, an inner end surface of the inner ring element 14b on the axially inner side abuts against a stepped surface (not shown) formed in a middle portion of the axle 11 via another annular member (not shown). Therefore, the paired inner ring elements 14a, 14b do not shift to a position which is closer to the center of the axle 11 (right side in FIG. 40) from the state in FIG. 40. A nut 17 which is screwed into an outer end portion of the axle 11 suppresses the annular member 16 towards the outer end surface of the inner element 14a on the axially outer side.
In addition, a detected ring or encoder ring 10 is made by a magnetic metal material such as a steel material and entirely formed into a circular shape in a L-shaped section, and fixed to one end surface of the axle 11. Recess sections and land sections are formed on an outer peripheral surface (outer peripheral edge) of the detected ring or encoder ring 10 alternatively with equal intervals in a circumferential direction, such that this outer peripheral surface has a gearing shape. Magnetic characteristics of the outer peripheral surface of the detected ring or encoder ring 10 are changed alternatively with equal intervals in the circumferential direction.
In addition, an opening at one end of the bearing housing 12 is covered by a cover 9 which is formed into a bottomed cylindrical shape by a synthetic resin or a metal material. Moreover, the rotation detecting sensor 3 is inserted into a sensor mounting hole 46 which is formed on a portion of a cylindrical portion 19 of the cover 9 opposed to the outer peripheral edge of the detected ring or encoder ring 10 in a diametrical direction. A detecting section provided on an end surface (lower end surface in FIG. 40) of the rotation detecting sensor 3 is opposed to the outer peripheral edge of the detected ring or encoder ring 10 via a gap.
Meanwhile, a sensor mounting concave hole 20 is formed on a middle portion of the bearing housing 12 and around the outer race 5. A temperature sensor 21 is installed into the sensor mounting concave hole 20.
In the case of the rotating and supporting apparatus with sensor having the above structure, when the detected ring or encoder ring 10 rotates at the time of driving together with the axle 11 to which the wheel is supported and fixed, the portion to be detected, specifically recess sections and land sections of the detected ring or encoder ring 10 pass alternatively through a vicinity of the detecting section provided on the end surface of the rotation detecting sensor 3. As a result, the density of a magnetic flux flowing in the rotation detecting sensor 3 changes, so that an output of the rotation detecting sensor 3 changes. A frequency with which the output of the rotation detecting sensor 3 changes in such a manner is proportional to the rotating speed of the wheel. Therefore, when the output of the rotation detecting sensor 3 is transmitted to a controller, not shown, the rotating speed of the wheel can be detected, and skidding of a rolling stock can be controlled suitably.
In addition, when rotational resistance of the double row rolling bearing 1 abnormally rises due to some reason such as skew of the rolling elements 8 and the temperature of the double row rolling bearing 1 rises, the temperature sensor 21 detects the temperature. A temperature signal detected by the temperature sensor 21 in such a manner is transmitted to a controller, not shown, and this controller gives a warning such that a warning lamp provided on a driver""s seat is lightened. When such a warning is given, a driver takes a measure such as emergency stop.
In the case of the example of the conventional structure shown in FIGS. 38 and 39, since the acceleration sensor 2 and the rotation detecting sensor 3 are supported to the outer race 5 by way of the cover 9, and the circular detected ring or encoder ring 10 is used, there is a possibility that state values of vibration, rotating speed and the like cannot be always measured accurately.
In addition in the case of the example of the conventional structure shown in FIGS. 40 and 41, since the rotation detecting sensor 3 and the temperature sensor 21 are independent, the mounting work of the sensors 3 and 21 and wiring work of a harness for taking out detecting signals of the sensors 3 and 21 become troublesome.
It can be considered that the structure of the example of FIGS. 38 and 39 is combined with the structure of the second example, namely, the rotation detecting sensor 3 and the temperature sensor 21 are combined so as to form a sensor unit, and the sensor unit is installed to the cover 9. However, in this case, consideration is required in order to effectively detect a temperature by mean of the temperature sensor 21.
The publication of Japanese Patent No. 2838701 describes a structure as shown in FIG. 42, in which a rotation detecting sensor 3 is fixed directly to an outer race 5, and the rotation detecting sensor 3 has a detecting surface (tip end surface) which is directly opposed to a section to be detected (outer peripheral edge) of a detected ring or encoder ring 10 externally fixed to a middle portion of an inner ring 7. However, in the example of the conventional structure described in the publication of Japanese Patent No. 2838701, only detection of a rotating speed of the inner ring 7 is taken into consideration, but vibration which is generated in the portion of double row rolling bearing 1 and measurement of the temperature of the portion of double row rolling bearing 1 are not taken into consideration.
In consideration of the problems described above, an object of this invention is to provide a rotation-speed sensor device that has construction for performing wireless transmission and that is capable of preventing faulty operation of the ABS or TCS.
The present invention is devised in order to solve the above problems and it is an object of the present invention to provide a double row rolling bearing with a sensor unit which is capable of accurately measuring two or more different kinds of state values such as rotating speed, vibration and temperature.